1. Field of the Invention
The invention relates to a method and an apparatus for presuming a light source color upon photographing in image data obtained by a digital camera or the like.
2. Related Background Art
The user can freely modify image data photographed by a digital camera or the like by using computer software called photo-retouching software. However, the modification of the image data to be seen as if an image were seen under a certain light source color requires of the user a sense of color and expertise, and without them, the modification of the image needs him to spend much labor and time. As a technique for solving such a problem, a color image converting apparatus for converting the image data to be seen as if under a desired light source color has been disclosed in JP-A-2001-245166.
According to the color image converting apparatus disclosed in JP-A-2001-245166, pixels which seem to be the light source color upon photographing are selected as candidate light source colors from the image data, a color adaptation model showing color adaptation of a sense of sight from the candidate light source colors to a desired predetermined light source color is used, and parameters of the color adaptation model which minimize an evaluating function for the color adaptation model are calculated. After that, the color image converting apparatus converts the image data to be seen as if under a desired light source color by using the color adaptation model shown by those parameters.
According to the foregoing conventional image converting apparatus, merely the selection of the candidate light source colors from the image data is disclosed and whether or not the selected candidate light source color corresponds to the light source color upon photographing is not presumed. For example, even when the selected candidate light source color differs from the light source color upon photographing, the image converting apparatus executes the converting process on the basis of the candidate light source color different from true values of the light source color, so that the image data cannot be converted into the data to be seen as if under the desired light source color.